Welcome

The title says it all: this blog features physics videos found everywhere on the web: animations, demonstrations, lectures, documentaries.

Please go here if you want to suggest other nice physics videos, and here if I mistakingly infringed your copyrights. If you understand French, you'll find a huge selection of physics videos in French in my other blog Vidéos de Physique.

Saturday, 31 May 2014

The essence of digital computing is the use of continuous physical states to represent a discrete number of symbols and the ability to perform logic based on those symbols. Although electronic circuits are exceptionally well-suited for this, any system that can handle symbols as both input and output is a digital computer.

Tuesday, 20 May 2014

A Rube Goldberg machine is a machine that accomplishes a simple task in as complicated a way as possible. Every year Purdue University holds a Rube Goldberg Machine Contest. Teams of college students from all over the country design and build these machines and enter them in the competition. We invited this year's winners from Purdue University to show off their creation on the show.

Friday, 16 May 2014

This supercomputer simulation shows one of the most violent events in the universe: a pair of neutron stars colliding, merging and forming a black hole. A neutron star is the compressed core left behind when a star born with between eight and 30 times the sun's mass explodes as a supernova. Neutron stars pack about 1.5 times the mass of the sun — equivalent to about half a million Earths — into a ball just 12 miles (20 km) across.

As the simulation begins, we view an unequally matched pair of neutron stars weighing 1.4 and 1.7 solar masses. They are separated by only about 11 miles, slightly less distance than their own diameters. Redder colors show regions of progressively lower density.

As the stars spiral toward each other, intense tides begin to deform them, possibly cracking their crusts. Neutron stars possess incredible density, but their surfaces are comparatively thin, with densities about a million times greater than gold. Their interiors crush matter to a much greater degree densities rise by 100 million times in their centers. To begin to imagine such mind-boggling densities, consider that a cubic centimeter of neutron star matter outweighs Mount Everest.

By 7 milliseconds, tidal forces overwhelm and shatter the lesser star. Its superdense contents erupt into the system and curl a spiral arm of incredibly hot material. At 13 milliseconds, the more massive star has accumulated too much mass to support it against gravity and collapses, and a new black hole is born. The black hole's event horizon — its point of no return — is shown by the gray sphere. While most of the matter from both neutron stars will fall into the black hole, some of the less dense, faster moving matter manages to orbit around it, quickly forming a large and rapidly rotating torus. This torus extends for about 124 miles (200 km) and contains the equivalent of 1/5th the mass of our sun. The entire simulation covers only 20 milliseconds.

Scientists think neutron star mergers like this produce short gamma-ray bursts (GRBs). Short GRBs last less than two seconds yet unleash as much energy as all the stars in our galaxy produce over one year.

The rapidly fading afterglow of these explosions presents a challenge to astronomers. A key element in understanding GRBs is getting instruments on large ground-based telescopes to capture afterglows as soon as possible after the burst. The rapid notification and accurate positions provided by NASA's Swift mission creates a vibrant synergy with ground-based observatories that has led to dramatically improved understanding of GRBs, especially for short bursts.

Wednesday, 14 May 2014

Scientists at MIT have traced 13 billion years of galaxy evolution, from shortly after the Big Bang to the present day. Their simulation, named Illustris, captures both the massive scale of the Universe and the intriguing variety of galaxies -- something previous modelers have struggled to do. It produces a Universe that looks remarkably similar to what we see through our telescopes, giving us greater confidence in our understanding of the Universe, from the laws of physics to our theories about galaxy formation.

In less than 100 seconds, Tim O'Brien of the University of Manchester in the UK provides a fly-by tour of pulsar science. When the first pulsar signal was detected in the 1960s, for a short time it was referred to as "little green man 1" because the regular pulsing appeared to be a message from aliens. However, it did not take long for astronomers to figure out that these signals come from rapidly rotating neutron stars, which beam radiation from their magnetic poles.

Thursday, 8 May 2014

"Prince Rupert's Drops are glass objects created by dripping molten glass into cold water. The glass cools into a tadpole-shaped droplet with a long, thin tail. The water rapidly cools the molten glass on the outside of the drop, while the inner portion of the drop remains significantly hotter. When the glass on the inside eventually cools, it contracts inside the already-solid outer part. This contraction sets up very large compressive stresses on the surface, while the core of the drop is in a state of tensile stress. It is a kind of toughened glass.

The very high residual stress within the drop gives rise to unusual qualities, such as the ability to withstand a blow from a hammer on the bulbous end without breaking, while the drop will disintegrate explosively if the tail end is even slightly damaged."

Scientists were shocked in 1998 when the expansion of the universe wasn't slowing down as expected by our best understanding of gravity at the time; the expansion was speeding up! That observation is just mind blowing, and yet it is true. In order to explain the data, physicists had to resurrect an abandoned idea of Einstein's now called dark energy. In this video, Fermilab's Dr. Don Lincoln tells us a little about the observations that led to the hypothesis of dark energy and what is the status of current research on the subject.

A bump on the head, a mysterious femme fatale and a strange encounter on a windswept peak all add up to a heck of a night for Manny Brot, Private Eye. Watch as he tries his hand at saving the dame and getting the cash! Shudder at the mind-bending geometric riddles! Thrill to the stunning solution of The Case of the Missing Fractals.